The Echinoids of Easter Island (Rapa Nui)

Abstract

The known echinoid fauna of Easter Island now comprises seven species. Four of them, Tripneustes gratilla, Echinostrephus sp., Clypeaster reticulatus, and Brissus agassizii are reported here from Easter Island for the first time, Tripneustes gratilla apparently being represented by a previously unknown variant. The value of the pedicellariae and the heavily plated peristome as specific differences in the genus Tripneustes is questioned. Comparison of Easter Island material with specimens from other parts of the Pacific supports the synonymy of Brissus meridionalis with Brissus agassizii. One of the previously reported species, Echinometra insularis, is herein restricted to Easter Island, reports of its occurrence elsewhere being based upon erroneous identifications. The reported occurrence of Diadema mexicanum at Easter Island is discounted.